Unless otherwise indicated herein, the materials described herein are not prior art to the claims in the present application and are not admitted to be prior art by inclusion in this section.
Optical discrete multitone (DMT) has become a candidate for next-generation short-reach and metropolitan area network fiber optic links. Due to its use of subcarriers, DMT may effectively equalize channel distortion with low computational complexity and limited noise enhancement. DMT may also have controllable information density across frequency, which allows efficient use of information capacity of channels with non-uniform magnitude. However, DMT may suffer from large peak-to-average-power ratio (PAPR), which may result in a need for a wider dynamic range in electronics that may include, but are not limited to, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and a modulator. This may be problematic for intensity-modulated direct-detection (IM-DD) DMT, since the high optical bias may also result in more shot noise and a larger relative intensity noise (RIN) penalty.
Quadrature amplitude modulation (QAM) techniques may include transmitting a sinusoid modulated in amplitude and phase by a sequence of complex symbols. The QAM techniques may have low PAPR compared to DMT. However, the QAM techniques may suffer noise enhancement from channels with large magnitude variations in frequency.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.